I recently upgraded my version of Community Answers and was also happy to see the SEF Advance plugin.

Unfortunately when I upload the sef_ext.php I get the following error.

Fatal error: Class 'sef_communityanswers' not found in /var/www/vhosts/XXXXXX/httpdocs/components/com_sef/sef_incl.php on line 0

Any suggestions?